In integrated circuits, the degree of integration has more and more increased and in the production of a semiconductor substrate such as VLSI, processing of super-fine patterns composed of line width having a half-micron or less has been required. In order to satisfy such a requirement, the wavelength of an exposure apparatus used for a photolithography has more and more shortened and at present, the use of a far ultraviolet light and an excimer laser (e.g., XeCl, KrF or ArF) is investigated. Furthermore, the formation of finer patterns by an electron beam or an X-ray has been investigated.
The electron beam lithography is regarded as the next generation pattern formation technique or the pattern formation technique after the next generation, and the development of a positive resist and negative resist having high sensitivity, high resolution and a rectangular profile forming property has been strongly desired.
According to the electron beam lithography, accelerated electron beams collide with atoms constituting a resist material and scatter to supply energy to compounds and as a result, the reaction of resist material occurs, whereby an image is formed. To use highly accelerated electron beams increases the rectilinear propagation of electron beams and decreases the influence of electron scattering so that it makes possible the formation of pattern having high resolution, rectangular profile and excellent edge roughness. On the other hand, however, the transmittance of electron beam increases, resulting in decrease in sensitivity. Thus, a trade off relation between the sensitivity and the resolution, resist profile and edge roughness exists in the electron beam lithography, and it is a problem to be solved to fulfill requirements for both the sensitivity and the resolution, resist profile and edge roughness. EUV lithography and X-ray lithography also have the same problem.
With respect to the positive resist for electron beam or X ray, resist techniques for KrF excimer laser have been mainly diverted and investigated. For instance, the combination use of a compound capable of generating an acid upon electron beam irradiation and an amine compound having a boiling point of not more than 250° C. as described in JP-A-2000-181065 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), the combination use of a polymer having an acid decomposable group, an acid generator and an electron beam sensitizer as described in European Patent 919, 867, and the combination use of a polymer having an acid decomposable group and an amide compound as described in JP-W-7-508840 (the term “JP-W” as used herein means an “unexamined published international patent application”) are known. Further, the use of a maleimide compound as described in JP-A-3-200968, the use of a sulfonamide compound as described in JP-A-7-92680, and the use of a sulfonimide compound including a partial structure of —SO2—NH—SO2— as described in JP-A-11-44950 are known. However, these attempts do not solve the problem to fulfill all requirements of high sensitivity, high resolution, good rectangular resist profile and excellent edge roughness.
On the other hand, with respect to chemical amplification negative resists, various alkali-soluble resins have been proposed. The use of polyvinyl phenol partially alkyl etherized is described in JP-A-8-152717. The use of copolymer of vinyl phenol and styrene is described in JP-A-6-67431 and JP-A-10-10733. The use of novolac resin is described in Japanese Patent 2,505,033. The use of monodispersed polyvinyl phenol is described in JP-A-7-311463 and JP-A-8-292559. However, it could not be achieved to fulfill all characteristics of the sensitivity, resolution, resist profile and edge roughness upon irradiation of electron beam or X-ray by using such alkali-soluble resins.
Also, various compounds capable of generating an acid upon irradiation of electron beam or X-ray have been proposed with respect to the chemical amplification negative resists. The use of organic halogen compound is described in JP-B-8-3635 (the term “JP-B” as used herein means an “examined Japanese patent publication”). The use of iodonium salt or sulfonium salt is described in JP-A-2-150848 and JP-A-6-199770. The use of acid generator containing Cl or Br is described in JP-A-2-52348, JP-A-4-367864 and JP-A-4-367865. The use of diazodisulfone or diazosulfone compound is described in JP-A-4-210960 and JP-A-4-217249. The use of triazine compound is described in JP-A-4-226454. The use of sulfonate compound is described in JP-A-3-87746, JP-A-4-291259, JP-A-6-236024 and U.S. Pat. No. 5,344,742. However, the trade off relation between the sensitivity and the resolution, resist profile and edge roughness upon irradiation of electron beam or X-ray cannot be overcome by using such acid generators.
Further, with respect to a crosslinking agent, for example, methylol melamine, a resole resin, an epoxylated novolac resin or a urea resin has been used. However, these crosslinking agents are unstable to heat and have a problem of preservation stability of a resist solution.
The resist compositions described in Japanese Patent 3,000,740, JP-A-9-166870 and JP-A-2-15270 are also insufficient for meeting characteristic requirements of high sensitivity, high resolution, good rectangular resist profile and excellent edge roughness upon irradiation of electron beam or X-ray.
Therefore, it is difficult to fulfill requirements for sufficiently high sensitivity, sufficiently high resolution, good rectangular resist profile and excellent edge roughness all together in hitherto known techniques and it has been strongly desired to solve the problem.